In JP 58-27453 Y, there is disclosed a structure (hereinafter referred to as a first conventional structure) in which a shaft, which is bifurcated and can be tapered by narrowing down a space therein, is elastically returned after passing through a hole in a body and is stopped from slipping off by a slip-off stopping lock provided at a tip portion thereof.
In JP 3796051 B, there is described a structure (hereinafter referred to as a second conventional structure) in which a shaft is provided with an arrowhead shaped engaging projection part at a tip thereof, and by closing a slit formed inside the engaging projection part, the shaft is configured to pass through an axis insertion hole in an elastically returnable manner.
Furthermore, in JP 4548911 B, there is introduced a structure (hereinafter referred to as a third conventional structure) in which a mushroom-shaped motor shaft has an abutting end part and a small-diameter shaft, and the abutting end part thereof is supported by a thrust washer. At this time, inside a small-diameter groove part surrounding the small-diameter shaft in a circumferential direction, there is a clip facing to stop the abutting end part from slipping off.
This clip includes four extension parts projecting out from a tubular base part toward a center in a transverse direction (a shaft-crossing direction). Each of the extension parts is elastically deformable, and by a tip of each of the extension parts, a space having a smaller diameter than that of the abutting end part is partitioned at the center.
Each of the extension parts, being pushed against the abutting end part, is deformed to allow for passage of the abutting end part, and is elastically returned after the passage so as to be engaged when the abutting end part is pulled up.
In other words, it is configured not to be engaged when it is supported by the thrust washer.
There are problems with the conventional structures, which are discussed as follows.
Since the shaft is bifurcated (and there is a wide space between the bifurcated parts) in the first conventional structure, there is a fear that overall shaft strength may be insufficient. It has a disadvantage in that the shaft may easily slip off in a case where one of the bifurcated parts of the shaft is damaged
The engaging projection part according to the second conventional structure is divided into two parts by the existence of a slit. Therefore, similar to the problem in the first conventional structure, there is a problem of insufficient strength and in that it may easily slip off.
The clip according to the third conventional structure is not related to a rotation of the shaft in the first place. The thrust washer is playing that role.
Therefore, there is a problem in that the number of components is increased.
Furthermore, it is necessary for the clip projecting in the transverse direction to receive a force from the shaft in a direction of pulling out with a thickness direction thereof.
There remains a need for improved shaft slip-off stopping structures and switches having such structures.